yeah, you can eventually kill your nemesis and create another one, I think there's a maximum of 10 killed or something, and you can't kill your last one, i don't know the specifics, but I got to 25 and picked pirates > claws > female (hawt costume)
and she gives me so much trouble, first the pirates have holds, lots of holds, like holdlocked, their holds dont add any resistance
not to mention the PvE claws users just keep spamming root on you,
my advice, don't pick pirates or claws lol